Obesity-associated extracellular mtDNA activates central TGFβ pathway to cause blood pressure increase

Mitochondrial DNA leakage triggers inflammation in age-related cardiovascular diseases

Mitochondrial dysfunction is one of the hallmarks of cardiovascular aging. The leakage of mitochondrial DNA (mtDNA) is increased in senescent cells, which are resistant to programmed cell death such as apoptosis. Due to its similarity to prokaryotic DNA, mtDNA could be recognized by cellular DNA sensors and trigger innate immune responses, resulting in chronic inflammatory conditions during aging. The mechanisms include cGAS-STING signaling, TLR-9 and inflammasomes activation. Mitochondrial quality controls such as mitophagy could prevent mitochondria from triggering harmful inflammatory responses, but when this homeostasis is out of balance, mtDNA-induced inflammation could become pathogenic and contribute to age-related cardiovascular diseases. Here, we summarize recent studies on mechanisms by which mtDNA promotes inflammation and aging-related cardiovascular diseases, and discuss the potential value of mtDNA in early screening and as therapeutic targets.

Increased levels of circulating oxidized mitochondrial DNA contribute to chronic inflammation in metabolic syndrome, and MitoQ-based antioxidant therapy alleviates this DNA-induced inflammation

Here, the aim was to investigate the role of circulating oxidized mitochondrial DNA (ox-mtDNA) in metabolic syndrome (MetS)-associated chronic inflammation and evaluate the effect of Mito-Quinone (MitoQ)-based antioxidant therapy on inflammation. A total of 112 MetS patients and 111 healthy control individuals (HCs) were recruited. Peripheral blood was collected, and mononuclear cells (PBMCs) were separated. In a preclinical study, MitoQ, a mitochondrial-targeted antioxidant, was administered to Sprague-Dawley (SD) rats fed a high-fat diet (HFD). In vitro, H₂O₂- or MitoQ-treated HUVECs served as the oxidative or antioxidative cell models to detect the cell-free ox-mtDNA level. Plasma or cell-free ox-mtDNA levels were measured by qPCR. Additionally, THP-1 cells were incubated with plasma cell-free DNA (cfDNA) from MetS patients and HCs or cell-free ox-mtDNA to detect TLR9-NF-κB pathway activation. Plasma ox-mtDNA levels and TLR9 expression levels in PBMCs were increased in MetS patients. In vivo, HFD-fed rats showed elevated plasma ox-mtDNA and TLR9 expression levels in cardiac-residing immune cells, but MitoQ administration attenuated these increases. In vitro, a significant lower level of cell-free ox-mtDNA was detected in MitoQ-treated cells, compared with H₂O₂-treated cells. Coincubation of plasma cfDNA from MetS patients or cell-free ox-mtDNA and THP-1 cells increased TLR9-NF-κB p65 expression, and promoted IL-1β, IL-6 and IL-8 secretion in THP-1 cells. In conclusion, increased circulating ox-mtDNA contributes to chronic inflammation in MetS by activating the TLR9-NF-κB pathway. MitoQ-based antioxidant therapy effectively alleviates inflammation by reducing ox-mtDNA release.

Identification of Key Genes from the Visceral Adipose Tissues of Overweight/Obese Adults with Hypertension through Transcriptome Sequencing

Overweight and obese (OW/OB) adults are at increased risk of hypertension due to visceral adipose tissue (VAT) inflammation. In this study, we explored gene level differences in the VAT of hypertensive and normotensive OW/OB patients. VAT samples obtained from six OW/OB adults (three hypertensive, three normotensive) were subjected to transcriptome sequencing analysis. Gene set enrichment analysis was conducted for all gene expression data to identify differentially expressed genes (DEGs) with |log2 (fold change)| ≥ 1 and q < 0.05. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes functional enrichment analyses were performed on the DEGs, and hub genes were identified by constructing a protein-protein interaction (PPI) network. The proposed hub genes were validated using quantitative real-time PCR in ten other samples from five hypertensive and five normotensive patients. In addition, we performed ROC analysis and Spearman correlation analysis. A total of 84 DEGs were identified between VAT samples from OW/OB patients with and without hypertension, among which 21 were significantly upregulated and 63 were significantly downregulated. Bioinformatics analysis revealed that spleen function was related to hypertension in OW/OB adults. Meanwhile, PPI network analysis identified the following top 10 hub genes: CD79A, CR2, SELL, CD22, IL7R, CCR7, TNFRSF13C, CXCR4, POU2AF1, and JAK3. Through qPCR verification, we found that CXCR4, CD22, and IL7R were statistically significant. qPCR verification suggested that RELA was statistically significant. However, qPCR verification indicated that NFKB1 and KLF2 were not statistically significant. These hub genes were mainly regulated by the transcription factor RELA. The AUC of ROC analysis for CXCR4, IL7R, and CD22 was 0.92. What is more, VAT CXCR4 and CD22 were positively related to RELA relative expression levels. Taken together, our research demonstrates that CXCR4, IL7R, and CD22 related to VAT in hypertensive OW/OB adults could serve as future therapeutic targets.

Contrasting effects of sleep fragmentation and angiotensin-II treatment upon pro-inflammatory responses of mice

Disordered sleep promotes inflammation in brain and peripheral tissues, but the mechanisms that regulate these responses are poorly understood. One hypothesis is that activation of the sympathetic nervous system (SNS) from sleep loss elevates blood pressure to promote vascular sheer stress leading to inflammation. As catecholamines produced from SNS activation can directly regulate inflammation, we pharmacologically altered blood pressure using an alternative approach-manipulation of the renin-angiotensin system (RAS). Male C57BL6/J mice were treated with angiotensin or captopril to elevate and reduce blood pressure, respectively and then exposed to 24-h of sleep fragmentation (SF) or allowed to sleep (control). Pro- and anti-inflammatory cytokine gene expression and as endothelial adhesion gene expression as well as serum glucocorticoids (corticosterone) were measured. RAS manipulation elevated cytokines and endothelial adhesion expression in heart and aorta while SF increased cytokine expression in peripheral tissues, but not brain. However, there were interactive effects of angiotensin-II and SF upon cytokine gene expression in hippocampus and hypothalamus, but not prefrontal cortex. SF, but not RAS manipulation, elevated serum corticosterone concentration. These findings highlight the contrasting effects of RAS manipulation and SF, implying that inflammation from SF is acting on different pathways that are largely independent of RAS manipulation.

Sex, Age, and Bodyweight as Determinants of Extracellular DNA in the Plasma of Mice: A Cross-Sectional Study

Extracellular DNA (ecDNA) is studied as a possible biomarker, but also as a trigger of the immune responses important for the pathogenesis of several diseases. Extracellular deoxyribonuclease (DNase) activity cleaves ecDNA. The aim of our study was to describe the interindividual variability of ecDNA and DNase activity in the plasma of healthy mice, and to analyze the potential determinants of the variability, including sex, age, and bodyweight. In this experiment, 58 adult CD1 mice (41 females and 31 males) of a variable age (3 to 16 months old) and bodyweight (females 25.7 to 52.1 g, males 24.6 to 49.6 g) were used. The plasma ecDNA was measured using a fluorometric method. The nuclear ecDNA and mitochondrial ecDNA were quantified using real-time PCR. The deoxyribonuclease activity was assessed using the single radial enzyme diffusion method. The coefficient of variance for plasma ecDNA was 139%, and for DNase 48%. Sex differences were not found in the plasma ecDNA (52.7 ± 73.0 ηg/mL), but in the DNase activity (74.5 ± 33.5 K.u./mL for males, and 47.0 ± 15.4 K.u./mL for females). There were no associations between plasma ecDNA and bodyweight or the age of mice. Our study shows that the variability of plasma ecDNA and DNase in adult healthy mice is very high. Sex, age, and bodyweight seem not to be major determinants of ecDNA variability in healthy mice. As ecDNA gains importance in the research of several diseases, it is of importance to understand its production and cleavage. Further studies should, thus, test other potential determinants, taking into account cleavage mechanisms other than DNase.

Mitochondrial DNA variation and the pathogenesis of osteoarthritis phenotypes

Mitochondria and mitochondrial DNA (mtDNA) variation are now recognized as important factors in the development of osteoarthritis (OA). Mitochondria are the energy powerhouses of the cell, and also regulate different processes involved in the pathogenesis of OA including inflammation, apoptosis, calcium metabolism and the generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS). Mitochondria contain their own genetic material, mtDNA, which evolved through the sequential accumulation of mtDNA variants to enable humans to adapt to different climates. The ROS and reactive metabolic intermediates that are by-products of mitochondrial metabolism are regulated in part by mtDNA and are among the signals that transmit information between mitochondria and the nucleus. These signals can alter nuclear gene expression and, when disrupted, affect a number of cellular processes and metabolic pathways, leading to disease. mtDNA variation influences OA-associated phenotypes, including those related to metabolism, inflammation and even ageing, as well as nuclear epigenetic regulation. This influence also enables the use of specific mtDNA haplogroups as complementary diagnostic and prognostic biomarkers of OA.

Gene-Level Regulation of Acupuncture Therapy in Spontaneously Hypertensive Rats: A Whole Transcriptome Analysis

Hypertension is a global health problem. It has been reported that acupuncture at Taichong acupoints (LR3) decreases high blood pressure in spontaneously hypertensive rats. A transcriptome analysis can profile gene expression and its relationship with acupuncture. In this study, rats were treated with 2 weeks of acupuncture followed by regular recording of blood pressure (BP). The mRNA changes in the rostral ventrolateral medulla (RVLM) were evaluated to uncover the genetic mechanisms of acupuncture by using a whole transcript array (Affymetrix Rat Gene 1.0 ST array). BP measurements showed that acupuncture significantly decreased systolic blood pressure (SBP), mean arterial pressure (MAP), and heart rate (HR). In the bioinformatics results, 2371 differentially expressed genes (DEGs) were identified, where 83 DEGs were overlapped among Wistar-Kyoto rats (WKYs), spontaneously hypertensive rats (SHRs), and SHRs + acupuncture rats (SHRs+Acu). Gene ontology (GO) and pathway analysis revealed that 279 GO terms and 20 pathways with significant differences were related to oxidative stress, inflammation, and vascular endothelial function. In addition, coexpressed DEGs networks indicated that Cd4 and Il-33 might mediate the cascade of inflammation and oxidative stress responses, which could serve as a potential target of acupuncture treatment. In conclusion, our study demonstrated that acupuncture is a promising therapy for treating hypertension and could regulate multiple biological processes mainly involving oxidative stress, inflammation, and vascular endothelial function.

Monocytes inhibit NK activityviaTGF-β in patients with obstructive sleep apnoea

Obstructive sleep apnoea (OSA) is associated with cancer incidence and mortality. The contribution of the immune system appears to be crucial; however, the potential role of monocytes and natural killer (NK) cells remains unclear.

Quantitative reverse transcriptase PCR, flow cytometry andin vitroassays were used to analyse the phenotype and immune response activity in 92 patients with OSA (60 recently diagnosed untreated patients and 32 patients after 6 months of treatment with continuous positive airway pressure (CPAP)) and 29 healthy volunteers (HV).

We determined that monocytes in patients with OSA exhibit an immunosuppressive phenotype, including surface expression of glycoprotein-A repetitions predominant protein (GARP) and transforming growth factor-β (TGF-β), in contrast to those from the HV and CPAP groups. High levels of TGF-β were detected in OSA sera. TGF-β release by GARP+monocytes impaired NK cytotoxicity and maturation. This altered phenotype correlated with the hypoxic severity clinical score (CT90). Reoxygenation eventually restored the altered phenotypes and cytotoxicity.

This study demonstrates that GARP+monocytes from untreated patients with OSA have an NK-suppressing role through their release of TGF-β. Our findings show that monocyte plasticity immunomodulates NK activity in this pathology, suggesting a potential role in cancer incidence.

Neural Programmatic Role of Leptin, TNFα, Melanocortin, and Glutamate in Blood Pressure Regulation vs Obesity-Related Hypertension in Male C57BL/6 Mice

Continuous nutritional surplus sets the stage for hypertension development. Whereas moderate dietary obesity in mice is normotensive, the homeostatic balance is disrupted concurrent with an increased risk of hypertension. However, it remains unclear how the obesity-associated prehypertensive state is converted into overt hypertension. Here, using mice with high-fat-diet (HFD)-induced moderate obesity vs control diet (CD)-fed lean mice, we comparatively studied the effects of central leptin and tumor necrosis factor-α (TNFα) as well as the involvement of the neuropeptide melanocortin pathway vs the neurotransmitter glutamate pathway. Compared with CD-fed lean mice, the pressor effect of central excess leptin and TNFα, but not melanocortin, was sensitized in HFD-fed mice. The pressor effect of central leptin in HFD-fed mice was strongly suppressed by glutamatergic inhibition but not by melanocortinergic inhibition. The pressor effect of central TNFα was substantially reversed by melanocortinergic inhibition in HFD-fed mice but barely in CD-fed mice. Regardless of diet, the hypertensive effects of central TNFα and melanocortin were both partially reversed by glutamatergic suppression. Hence, neural control of blood pressure is mediated by a signaling network between leptin, TNFα, melanocortin, and glutamate and changes in dynamics due to central excess leptin and TNFα mediate the switch from normal physiology to obesity-related hypertension.

The Gut, Its Microbiome, and Hypertension

PURPOSE OF THE REVIEW

Evidence is rapidly accumulating implicating gut dysbiosis in hypertension (HTN). However, we are far from understanding whether this is a cause or consequence of HTN, and how to best translate this fundamental knowledge to advance the management of HTN. This review aims to summarize recent advances in the field, illustrate the connections between the gut and hypertension, and establish that the gut microbiota (GM)-gut interaction is centrally positioned for consideration as an innovative approach for HTN therapeutics.

RECENT FINDINGS

Animal models of HTN have shown that gut pathology occurs in HTN, and provides some clues to mechanisms linking the dysbiosis, gut pathology, and HTN. Circumstantial evidence links gut dysbiosis and HTN. Gut pathology, apparent in animal HTN models, has not been fully investigated in hypertensive patients. Objective evidence and an understanding of mechanisms could have a major impact for new antihypertensive therapies and/or improved applications of current ones.